Although the forward/reverse planetary gearset system of this disclosure is broadly applicable to numerous fields of use, an automotive point of reference will be used to provide an initial context for introducing the disclosed gearset system, albeit by way of example only.
An automotive vehicle typically includes an internal combustion engine containing a rotary crankshaft configured to transfer motive power from the engine through a driveshaft to the wheels. A transmission is interposed between engine and driveshaft components to selectively control torque and speed ratios between the crankshaft and driveshaft. In a manually operated transmission, a corresponding manually operated clutch may be interposed between the engine and transmission to selectively engage and disengage the crankshaft from the driveshaft to facilitate manual shifting among available transmission gear ratios.
On the other hand, if the transmission is automatic, the transmission will normally include an internal plurality of automatically actuated clutches adapted to dynamically shift among variously available gear ratios without requiring driver intervention. Pluralities of clutches, also called clutch modules, are incorporated within such transmissions to facilitate the automatic gear ratio changes. Finally, a torque converter may also be interposed between the engine and transmission systems, as those skilled in the art will appreciate.
In an automatic transmission of an automobile, numerous forward gear ratios are generally selectively available, along with at least one reverse gear. The various gears within the automatic transmission are typically comprised of planetary gearsets, including sun and planetary pinion gears supported by carriers, all movable with respect to one another as well as within and relative to so-called ring gears. Specific transmission clutches are typically associated with specific sets of the selectable gears within the transmission to facilitate the desired ratio changes.
For accommodating multiple gear ratios, the planetary gearsets are often used in combination with at least two friction clutches to manage directional control. One such friction clutch is adapted to handle the forward gear ratios, while the second is adapted to handle reverse gear ratios.
The friction clutches are typically hydraulically operated disc clutches, in which a set of interleaved friction discs and separator plates are splined to hub and drum components, respectively. The clutch is engaged and disengaged by means of an actuating piston, as those skilled in the art will appreciate. A common problem with this type of clutch is its tendency to develop parasitic drag, particularly when the friction discs and separator plates fail to fully disengage. Another problem relates to their bulkiness, especially because their associated pistons and springs may require special packaging and sizing considerations.